It’s hard to remember the last time it felt this good to be a eurosceptic, to love Europe but abhor the mid-century anachronism that is the European Union.

Since the dying days of the Major government we eurosceptics have been on the back foot, forced to watch Britain sign the agreements and ratify the treaties which lashed us ever more tightly to the post-war dream of ever-closer union, totally incapable of mounting an effective defence. And when we did speak up, we have consistently been portrayed as cranks and obsessives.

Aside from the recent morale boost courtesy of Nigel Farage and UKIP, it has often felt as though we eurosceptics were waging a lonely and futile battle against progress itself – against the inevitability of a world of huge, supranational, protectionist trading blocs, with nation states stripped of power and relevance, and representative democracy a thing of the past.

But not now, not in 2015. Not after Greece.

It should not have taken the immolation of a small, southern European country – sacrificed for the “greater good” of monetary union – for so many people to finally wake up and realise that the European Union does not mean them well, that the Eurogroup’s treatment of one recalcitrant member is the rule, not the exception.

No, it should not have taken the subjugation of Greece for others to realise this truth. But there has been a certain satisfaction in watching the ranks of europhiles and virtue-signalling internationalists go through the five stages of grief as their belief in the EU ebbed away, and then gradually flirt with turning to the ‘dark side’ of euroscepticism.

Owen Jones may be the poster boy of new converts, but he is far from the only one. Across the Atlantic, the overrated economist Paul Krugman – ever eager to force unwanted political union on countries other than his own – was forced to eat his words when it became clear that the benign Europe he loved to champion was behaving like an irrational bully. And closer to home, growing numbers of Guardian finger-waggers and left-wing bloggers are coming to the same conclusion.

But it is not just the Labour Left who are giving up on the European dream. The general public, raised on the narrative that the EU stands for enlightened internationalism and a common European identity, have now seen for themselves what happens when one member state tries to stand up for their own national interest, and the British people will take their lesson from Greece’s crucifixion.

This represents a genuine opportunity for eurosceptics to seize the initiative ahead of the coming Brexit referendum in 2016/17. In her overrated maiden speech to parliament, the SNP’s Mhairi Black talked about politicians either being weather vanes, twisting and turning with public opinion, or signposts, true to their convictions and pointing the right way ahead in all weathers.

For all of their political calculation and electoral success, nobody can accuse David Cameron or George Osborne (who will be leading Britain’s renegotiation with the EU) of being signposts. The Conservative Party is in the hands of political weather vane.

Fortunately, thanks to the inevitable failure of monetary union, and the tone-deaf intransigence of Germany, a strong eurosceptic wind is now blowing across the land. Until now, it was almost certain that David Cameron would make a half-hearted attempt to claw back a few superficial concessions from Brussels before presenting them as a great triumph of diplomacy and lobbying hard for Britain to remain within the European Union.

But now that a sizeable and newly emboldened eurosceptic faction exists at both ends of the political spectrum – with UKIP having won four million votes in the general election, and the Owen Jones Left of the Labour Party now openly calling for Brexit – this is no longer a foregone conclusion.

No doubt Cameron’s preferred outcome is still for a quick renegotiation and a campaign for “In”, but more than anything the prime minister wants to be on the winning side. If the EU continues to sabotage its own credibility through mismanagement of the Greek crisis, the political calculus may yet shift to the extent that it becomes prudent for David Cameron to actually do what a Conservative leader should do without prompting, and stand up for Britain’s national interest and freedom from an unwanted political union with Europe.

How can we make this come about? First, we must do what eurosceptics have always struggled to do – put ego aside and work together towards the common goal. This means a pragmatic cessation of hostilities between the Conservatives and UKIP until the polling stations close on referendum day.

It also means getting used to fighting alongside some unexpected allies. Many of us approach the issue of Europe and national sovereignty from a pro-liberty, small government perspective – we oppose the European Union because it represents unaccountable big government and a deadly threat to the nation state, the guarantor and protector of our freedoms. But now we must welcome legions of disaffected left-wingers, newly willing to fight under our banner.

Their vision for Britain and the world may be totally different to our own, but we do share one vital thing in common: the belief that it should be up to the British to choose their own destiny, and that our democratic choices should not be subject to veto or amendment by unaccountable forces in Brussels.

Here, we can learn from UKIP, who began as a small-government, single-issue party with a wonkish obsession with one burning constitutional question – who governs Britain? But UKIP’s rise, particularly since 2013, has been driven by the Left’s disdain for Labour just as much as the Right’s despair at Cameron’s style of conservatism. Nigel Farage, for all his flaws, has managed to create a big tent capable of accommodating libertarians, social conservatives and disaffected Old Labour types – and in the 2014 and 2015 elections, he turned this unlikely alliance into four million votes.

This is exactly what we eurosceptics must all work to achieve if we are to seize this opportunity and strike back while the EU is gridlocked and weak, its protagonists snarling, selfish and sullied in the eyes of the global community.

We come from diverse backgrounds and very different political traditions. We can count big business, entrepreneurs, small traders, trade unionists, free marketers, libertarians, social conservatives and traditionalists among our number. We will never agree on everything, but we are all of the belief that we will never truly be free so long as our country is just a star on someone else’s flag.

Some of us have held this belief for many years, and have been fighting the good fight for as long as we can remember, with precious little acknowledgement or reward. Others among us, particularly those on the Left, have been slower to see the light. But now is not the time to gloat or admonish those whose deeply held left-wing principles have only now forced them to question their instinctive support for a united Europe.

Through its supreme arrogance and unconscionable treatment of Greece – a member of the European Union ‘family’ – the EU has at a stroke created hundreds of thousands of new British eurosceptics, and potentially millions more people who are now open to persuasion for the first time.

Shakespeare was right when he wrote “there is a tide in the affairs of men, which, taken at the flood, leads on to fortune”. And as we eurosceptics seek to undo the harm wrought upon our sovereignty by the Treaty of Rome and its successors, we cannot afford to let this unprecedented high tide pass us by.

Sam Hooper is a journalist and blogger. He writes about politics, economic and personal freedom, civil liberties and classical music.